In the manufacture of a number of paper products such as hand towels, wipers and the like, a wide variety of product characteristics must be given attention in order to provide a final product with the appropriate blend of attributes suitable for the product's intended purposes. Among these various attributes, improving strength, absorbency, caliper and stretch have always been major objectives, particularly for products sold and used in the service and industrial markets. Traditionally, many of these paper products have been made using a wet-pressing process in which a significant amount of water is removed from a wet laid web by pressing or squeezing water from the web prior to final drying. In particular, while supported by an absorbent papermaking felt, the web is squeezed between the felt and the surface of a rotating heated cylinder (Yankee dryer) using a pressure roll as the web is transferred to the surface of the Yankee dryer. The web is thereafter dislodged from the Yankee dryer with a doctor blade (creping), which serves to partially debond the web by breaking many of the bonds previously formed during the wet-pressing stages of the process. The web can be creped dry or wet. Creping generally improves the softness of the web, but at the expense of a significant loss in strength.
More recently, throughdrying has become a more common means of drying paper webs. Throughdrying provides a relatively noncompressive method of removing water from the web by passing hot air through the web until it is dry. More specifically, a wet-laid web is transferred from the forming fabric to a coarse, highly permeable throughdrying fabric and retained on the throughdrying fabric until it is dry. The resulting dried web is softer and bulkier than a conventionally-dried uncreped sheet because fewer bonds are formed and because the web is less compressed. Squeezing water from the wet web is eliminated, although the use of a pressure roll to subsequently transfer the web to a Yankee dryer for creping may still be used.
While there is a processing incentive to eliminate the Yankee dryer and make an uncreped throughdried product, uncreped throughdried sheets are typically stiff and, if not calendered, rough to the touch compared to their creped counterparts. This is partially due to the inherently high stiffness and strength of an uncreped sheet, but is also in part due to the coarseness of the throughdrying fabric onto which the wet web is conformed and dried. As a consequence, the use of uncreped throughdried sheets has been heretofore limited to applications where high strength is paramount. These products have moderate absorbency properties.
Therefore there is a need for an uncreped throughdried paper product with an improved blend of properties for use as a wiper or paper towel.